1. Field of the Invention
The present invention pertains to the inspection of sealed packages and, more particularly, to the inspection of the integrity of sealed packages. The invention has particular application in inspecting the integrity of sealed packages containing food products, e.g., snack food products such as potato chips or the like.
2. Description of Related Art
It is generally known in the prior art to inspect sealed packages in order to determine the presence of packages having leaks therein, i.e., packages which are improperly or inadequately sealed. One such apparatus is disclosed in U.S. Pat. No. 4,148,213. The '213 apparatus conveys sealed packages between a pair of conveyor belts in order to determine the presence of leaky packages. The upper conveyor belt is spring biased in a downward direction toward the lower conveyor belt. As the packages enter the space between the two conveyor belts, the upper belt is pushed upward against the force of the spring such that the packages are clamped between the two belts. Only packages which are sealed will push the upper belt upward and will be clamped between the two belts. When a package having a leak moves between the two conveyor belts, the upper belt is not forced upwardly and the bag is not suitably clamped between the two belts. An air nozzle is mounted adjacent to the space between the two belts. The air nozzle blows air against a package located between the two belts. A package which does not contain a leak is sufficiently clamped between the two belts (due to the spring force) so as to prevent the package from being blown from between the belts. However, when a leaky package is located between the two belts, the air blown from the nozzle contacts the package and removes it from the conveyor belt. The leaky package is not clamped between the two belts with sufficient force to prevent it from being removed by the blast of air.
Another prior art device is disclosed in U.S. Pat. No. 4,697,452. The '452 apparatus includes a first conveyor belt which conveys sealed packages horizontally and underneath a pair of overlying spaced pressure belts. A gap is formed between the two pressure belts and the underlying conveyor belt through which the packages pass. A V-shaped arm is disposed in the space between the two pressure belts and extends downward into the gap so as to contact the packages moving along the lower conveyor belt. The bags conveyed by the lower conveyor belt are engaged by the pressure belts which stretch the bags taut if the bags have no leaks. A light source and photocell detect the presence of a bag and transmit a signal to remove the bag. When a bag with no leaks is located between the belts, the V-shaped arm is moved upward by the taut bag and interrupts a light beam so as to prevent the good bag from being removed. When a bag with a leak passes between the belts, the V-shaped arm is not pushed upward a sufficient distance to interrupt the light beam and thus the signal sent by the light source to the photocell results in the removal of the leaky bag.
Although considerable work has been done in the art in order to achieve systems for inspecting the integrity of sealed packages, there remains room for improvement. For example, the patents described above disclose relatively complex devices which may be susceptible to mechanical breakdown. The apparatus disclosed in the U.S. Pat. No. 4,148,213 patent includes a pair of cylinders and piston rods which control movement of the upper conveyor belt. The cylinders contain springs which bias the piston rods downward, the upper conveyor belt being connected to the piston rods. Potential problems with this apparatus include the possibility that the pistons will get out of phase with one another which would result in the upper belt being improperly moved or located relative to the lower belt. This could adversely affect the clamping pressure applied to the bags which in turn could lead to good packages being removed by the blast of air.
Likewise, the device disclosed in the U.S. Pat. No. 4,697,452 patent is a relatively complex, cumbersome system as it includes a pair of separate pressure belts disposed to overlie a package carrying conveyor belt, with a boomerang-shaped arm pivotally mounted in a gap form between the pressure belts. Potential problems in the operation of this apparatus include the possibility that the pair of overlying pressure belts could get out of sync or otherwise engage the packages in an inconsistent manner. This could result in the packages being improperly conveyed and inadequately engaging the V-shaped arm which may result in inaccurate detection of leaky packages.
In addition, the devices of the above patents do not conduct leak detection as accurately and as quickly as desired under many industry conditions. There remains a need for an improved apparatus and process for detecting the presence of improperly or inadequately sealed packages.